1. Field of the Invention
The present invention relates to a liquid crystal display device (LCD), and more particularly, to an in-cell touch type LCD.
2. Discussion of the Related Art
Recently, LCDs have been spotlighted as next generation high-tech display devices of low power consumption, good portability, high added value and the like.
Among the LCDs, active matrix type LCDs are widely used, which includes a thin film transistor (TFT) in each pixel.
The LCD is applied to various appliances such as TV, projector, mobile phone and PDA, and the appliances have a touch function to touch a screen and conduct an operation.
An LCD having a touch function embedded therein is referred to as an in-cell touch type LCD.
The in-cell touch type LCD includes gate and data lines, and additionally, touch blocks to sense a touch and touch lines connected to the touch blocks.
In the in-cell touch type LCD, a common electrode is supplied with a common voltage for a display period to display an image. The common electrode functions as a touch electrode to sense a touch for a non-display period not to display an image.
Accordingly, when a user touch a touch region, for example, using a user's finger, a touch capacitance is produced between common electrodes which are separately formed at respective touch blocks. A touch position is detected by comparing the touch capacitance by the user's touch with a reference capacitance, and an operation according to the touch position is conducted.
In this regard, by comparing the touch capacitance with the reference capacitance, a coordinate where the user's touch happens is recognized, and then an operation corresponding to the coordinate is conducted.
Accordingly, a touch line, which transmits change of capacitance of a common electrode formed at each touch block to a sensing circuit portion that is located at a non-display region or printed circuit board, is required. Since the touch line is connected to the common electrode, the touch line cannot be formed at the same layer as the common electrode.